1. Field of the Invention
The present invention relates to an image processing device and an image processing method, and an image forming apparatus, which are suitable for image forming onto a printing medium.
2. Description of the Related Art
In the fields of page printers or the like, high resolution printing and high speed printing are conventionally required. However, these requirements become harder to be satisfied only by performances of CPUs (Central Processing Unit) for controlling operations of printers. Particularly, in color printers, numerous processing such as drawing processing for respective color component images of Cyan (C), Magenta (M), Yellow (Y) and Black (K), color conversion processing, and halftoning (also called a halftone processing) are required in addition to various image processing.
A conventional printing operation can be schematically described as follows. Data such as PDL (Page Description Language) data generated by a personal computer (PC) or the like is transferred to a printer via a predetermined interface such as network and cable. The printer analyzes the transferred PDL data to generate an intermediate language executable by a drawing unit of the printer. The drawing unit analyzes the generated intermediate language to generate image data, and performs a gradation processing on the generated image data to obtain binary image data. The binary image data is drawn to a band memory so that the binary image data is stored in the band memory. The image drawing is performed for each color component image of C, M, Y and K.
The printer encodes the each color component image data drawn to the band memory according to a binary image compression algorithm such as JBIG (Joint Bi-level Image Coding Expert Group), and writes the encoded data into the memory for each color component. When printing, the printer reads the encoded data from the memory delayed for each color component image of C, M, Y and K to decode the data. The printer transfers the decoded data to a printer engine corresponding to each of C, M, Y and K, so that the printing is performed.
A halftoning is one of gradation processing to convert multivalued gradation image data into binary image data suitable for the printing. According to the halftoning, a binary pattern corresponding to the gradation value is applied to the multivalued gradation image data having gradation tone or the like. It is possible to obtain the binary image corresponding to the desired gradation value by changing the proportion of the binary pattern in a predetermined area.
With regard to the halftoning, for example, Japanese Patent No. 3446324 discloses, a technique in which a halftone pattern is generated by performing a bit shifting of a basic pattern of a halftone pattern, and a drawing unit is started to draw the generated halftone pattern by means of a halftone repeating function, so that the halftone pattern is generated by means of the least common multiple of a basic bit pattern width and a memory boundary width of the drawing unit.
Furthermore, for example, Japanese Patent No. 4490783 discloses a technique in which at least Y width of a halftone pattern having a drawing word X width is stored into a halftone storage unit, and a cyclic shift processing corresponding to a halftone pattern shift value is performed by using the halftone pattern corresponding to a halftone pattern address value. According to the Japanese Patent No. 4490763, it is possible to repeatedly use the halftone pattern for drawing objects having the same gradation value. Therefore, different from Japanese Patent No. 3446324, the memory capacity can be saved without generating the halftone pattern by means of least common multiple of the basic bit pattern and the memory boundary width of the drawing unit.
On the other hand, a brush treatment is one of image processing in printers. The brush treatment is a treatment or processing to perform the drawing by generating desired colors from each color of R, G, and B, for example.
In the image processing in printers, conventionally, the drawing is performed through the brush treatment, and the drawn image data is subjected to the gradation processing by halftoning. Namely, one page image is subjected to the brush treatment, and this brush treated one page image is subjected to the halftoning. Thereby, a memory is required which can store one page image data. This raises the cost.
Therefore, a brush treatment is conventionally known in which a first color illustrated in FIG. 20B and a second color illustrated in FIG. 20C are respectively applied to binary brush pattern values “1” and “0” illustrated in FIG. 20A, so that the first color and the second color is selectively drawn.
In the technique of Japanese Patent No. 4490783, the halftoning repeatedly uses the halftone pattern. Therefore, the required memory capacity can be reduced. However, the Japanese Patent No. 4490783 does not disclose the brush treatment at all. Therefore, it was difficult to apply the technique disclosed by Japanese Patent No. 4490783 to the brush treatment illustrated by using FIG. 20.